Evaluation of Some Radioisotopes as Marking Agents for Monitoring Bait Consumption

Minute quantities (1 to 20 μCi) of six gamma-emitting radioisotopes, manganese-54, zinc-65, selenium-75, iodine-125, iodine-131, and cesium-134, incorporated into nontoxic baits were found suitable as marking agents to detect bait consumption by coyotes (Canis latrans). The small quantity of isotope required minimizes detection of the marker by coyotes and potentially provides a bias-free procedure for simultaneously comparing the relative efficiency of several bait delivery techniques. Presence and identity of specific markers were determined with a multichannel analyzer on the basis of the energy level of emitted radiation. Differences in relative distribution of these isotopes among body tissues were noted. Other potential applications and constraints are discussed.